quiver to show the magnitude of velocity

Question

Changoleon 2016-11-25

0
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此问题的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313983-quiver-to-show-the-magnitude-of-velocity

编辑： Changoleon 2016-11-25

采纳的回答： Changoleon

在 MATLAB Online 中打开

Hi all,

I have the following:

x=1;
y=1;
u=3;
v=4;
w = sqrt(u^2+v^2);

now if I use quiver(x,y,u,v) and click on the arrow by cursor, I will have x and y along with velocities in x and y axis are going to be shown. I want to my cursor to show the magnitude of the velocity which is w. For that I have watched the following video and tried to do the same job.

http://blogs.mathworks.com/videos/2011/02/25/creating-a-custom-data-cursor/

Following is what I have done:

function moneyplot(x,y,u,v)
fh = figure;
quiver(x,y,u,v,0)
dcm = datacursormode(fh);
datacursormode on
set(dcm, 'updatefcn', @myfunction)
end
function output_txt = myfunction(obj,event_obj,w)
pos = get(event_obj,'Position');
output_txt = {['velocity= ',w]};
if length(pos) > 2
    output_txt{end+1} = ['Z: ',num2str(pos(3),4)];
end

However now every time I use the cursor to choose the arrow it shows : Error in custom datatip string function. Please see the picture below. What am I doing wrong?

Will be apreciated for any kinda input.

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Answer 1

Changoleon 2016-11-25

0
链接

此回答的直接链接

https://ww2.mathworks.cn/matlabcentral/answers/313983-quiver-to-show-the-magnitude-of-velocity#answer_244720

编辑：Changoleon 2016-11-25

在 MATLAB Online 中打开

I did not find the answer to my question. Here is what I have done and it kinda works, better than nothing

clc
x=[1 2 3 4 5];
y=[1 2 3 4 5];
u=[3 3 3 3 3];
v=[4 4 4 4 4];
 quiver(x,y,u,v,0)
for i = 1:5
[xx,yy] = ginput(2);
velocity=sqrt((xx(2)-xx(1))^2 + (yy(2)-yy(1))^2);
strmin = ['Velocity = ',num2str(velocity),' m/s',[1 1 1]];
t = text(xx(1),yy(1),strmin,'HorizontalAlignment','left');
s = t.FontSize;
t.FontSize = 12;
end